System of motor control.



A. M. GRAY.

SYSTEM OF MOTOR CONTROL.

APPLICATION FILED SEPT- 24, I9IO.

Patented Sept. 19, 1916.

UNITED STATES PATENT OFFICE.

I nmixnrinnn u. GRAY, or MILWAUKEE, WISCONSIN, ASSIGNOR, BY misnn ASSIGN- MENTS, TO ALLIS-CHALMERS MANUFACTURING COMPANY, A CORPORATION OF DELAWARE.

SYSTEM or Moron conraon Specification of Letters Patent.

PatentedSept. 19, 1916.

To all whom it ma concern."

Be it known that I, ALEXANDER M. GRAY, a subject of the King of England, residing at Milwaukee, in the county of Milwaukee and State of Wisconsin, have invented certain new and useful Improvements in Sys toms of Motor Control, of which the following is a full, clear, and exact specification.

My invention relates to motors, and more particularly to means for starting induction motors having rotating members of considerable inertia. 4

In many electrical systems it is necessary that the rotating mass have considerable inertia, as, for instance, in fiy-wheel balancer systems where a motor driving a flywheel is connected across the circuit to maintain the load on the generator supplying such circuit constant. In starting a motor havlng such a rotating member, a very large current" is requlred for a consid- 'erable period of time, and as the speed of the'motor during such time is low, and the ventilation therefore poor, the motor will heat excessively and the insulation is apt to be destroyed. a

It's the object of my invention to obtain a simple and reliable arrangement for starting a motor having a rotating member of considerable inertia. In attaining this object a device is used by which the motor is started and allowed .to accelerate until its temperature has reached the maximum ermissiblevalue, after which it is allowe to coast and thereby cool itself. A cycle of i this kind is repeated until the heavy rotating member has attained approximately the desired speed. In the arrangement illustrated, the motor is of the squirrel cage induction type, but other types of motors may be used.

The various novel features of my invention will be described in the specification, illustrated in the drawings, and particularly set forth in the appended claims.

Figure 1 of the drawings shows semi" diagrammatically one embodiment of my invention; and, Fig. 2 shows an end view of the switch-actuating device. a

The motor, 10, here shown asa squirrel wheel 14 mounted on the motor shaft 15.

Extending from the end of the shaft 15 is a pin 16 having gear 17 slidably mounted thereon and capable of being moved longitud nally by a handle 18 pivoted on an incloslng casing 19. A gear 20, capable of being driven by the gear 17 and carrying a bridging contact 21, is mounted on a in 20 secured to the'casing 19. The bridglng contact 21 cooperates with two stationary arc-shaped contacts 22 and 23 mounted upon and insulated from the casing 19., In the leads 11 12 and 13 is a switch 26, which is normall biased to open position, as by a spring 2 but movable to closed position by a solenoid 25. The switch 26 may be of any desiredtype of anti-sparking switch, for instance, an oil switch, or a switch having blowout magnets, may be used. The solenoid 25 is connected to the contacts 22 and 23 and to a storage battery 24 so that it is energized when the bridging contact 21 engages the contacts 22 and 23. Included in the circuit of the storage battery 24 is a switch 28, which, if open, allows the switch 26 to be opened regardless of the position of the bridging contact 21. v

When the motor 10 is at rest, the switches 26 and 28 are in the positions shown in Fig. 1. Before starting the motor 10, the gear 1?, if in engagement with the gear 20,

i is moved to the left by means of the handle .18 and the bridging contact 21 is moved in a bridging contact 21. is moved across the contacts 22 and 23 by means of the gear 20 driven by the motor through the gear 17.

l The motor 10, because it is rotating very circuit of the solenoid 25. The switch 26 is now opened by means of the spring 27 and the motor is allowed to coast and thereby cool itself. The switch 26 remains open until the motor 10, coasting, has brought the bridgin contact 21 again into engagement with t e contacts 22 and 23, when the solenoid 25 is again energized and the switch 26 again closed to complete the circuit of the motor 10. The motor now accelerates further, for during the time the motor was allowed to coast, very little speed was lost. By repeating the foregoing cycle a sufiicient number'of times, the motor 10 will, without [excessive heating, accelerate the fly-wheel 14- to the required speed. When the motor 10 has reached the desired speed, the switch 28 is moved to the right into engagement with the contact 28* to close the circuit through the solenoid 25 independently of the contacts 21, 22, and 23, thereby allowing the switch 26 to remain permanently in a closed position. At the same time the handle 18 may be moved to the right to disengage the gear 17 from the gear 20.

Many modifications may be made in the precise form and arrangement shown and described, and I aim in my claims to cover all such modifications which do not involve a departure from the spirit and scope of my invention.

What I claim as new is:

1. In combination, an induction motor having a rotating member of large inertia, a switch in the supply circuit of said motor and which'is normally biased to open position, means controlled by said motor for closing said switch, and means for rendering said first named means inoperative.

2. In combination, an induction motor having a rotating member of large inertia, a switch in the motor supply circuit, means controlled by said motor for' closing and opening said switch, and means for rendermg said first named means inoperative "when said motor has gained the desired speed.

3. In combination, a motor having a shaft, a member of great inertia carried thereby, a switch for controlling the circuit of said motor, means controlled by the motor for operating said switch to open and closed-positions during the acceleration of said motor, and means for rendering said means inoperative.

4. In combination, a motor, a switch in the supply circuit of said motor normally biased to open position, means controlled by said motor for closing said switch, and means for rendering said first named means inoperative.

5.- In combination, a motor, a switchin the motor supply circuit, means controlled by said motor for closing and opening said switch, and'means for rendering said first named means inoperative when said motor has gained the desired speed.

6; In combination, a motor, a member of great inertia rotated thereby, a switch in the supply circuit of said motor, means controlled by said motor and operative to hold saidv switch closed and open for appreciable intervals of time during the acceleration of said motor from rest to normal operating speed, and means for rendering said first mentioned means ineffective for control purposes and permitting said switch to remain closed when said motor reaches normal operating speed.

7,. In combination, an induction motor and a rotating member of great inertia directly connected thereto, a switch in the supply circuit of said motor, means for accelerating said motor from rest to normal operating speed comprising meansfor auto matically closing and opening said switch to allow the motor to coast a portion of the time to cool the motor parts, and means for rendering said first mentioned means ineffective for control purposes and permitting said switch to remain closed during normal operation of said motor.

8. In combination, a motor having a rotating member of great inertia, means for accelerating said rotating member from rest .to normal operating speed comprising a switch in the motor supply circuit, means operative by said motor to hold said switch in closed and open positions for appreciable intervals of time, and means effective to hold said switch closed when said motor is operating at normal speed.

9. In combination, a motor having a rotating member of great inertia, means for accelerating said rotating member from rest to normal operating speed comprising a con- I 11. In combination, an electric motor, Milwaukee wisg sept. 2d 1910.

- means for decreasing and increasing the In testimony whereof I aflix my signature,

supply of energy to said motor, means conin the presence of two witnesses.

' trolled by said motor for causing operation ALEXANDER M. GRAY.

of said energy varying means during accel- Witnesses: eration, and means for rendering said motor JOHN L. JO NSON,

controlled means ineifective. CHAS. L. BYRON. 

